guiprocess: Improve output for crashing processes

Before this change, we displayed two different error messages, one in
_on_error, one in _on_finished. See the screenshot here:
https://www.reddit.com/r/qutebrowser/comments/kwvaw8/setting_vim_as_editor_creates_error_message/

2 files changed, 18 insertions, 3 deletions

diff --git a/qutebrowser/misc/guiprocess.py b/qutebrowser/misc/guiprocess.py
index 872a594f3..00948fe13 100644
--- a/qutebrowser/misc/guiprocess.py
+++ b/qutebrowser/misc/guiprocess.py
@@ -75,9 +75,12 @@ class GUIProcess(QObject):
                 procenv.insert(k, v)
             self._proc.setProcessEnvironment(procenv)
 
-    @pyqtSlot()
-    def _on_error(self):
+    @pyqtSlot(QProcess.ProcessError)
+    def _on_error(self, error):
         """Show a message if there was an error while spawning."""
+        if error == QProcess.Crashed:
+            # Already handled via ExitStatus in _on_finished
+            return
         msg = self._proc.errorString()
         message.error("Error while spawning {}: {}".format(self._what, msg))
 
@@ -101,7 +104,7 @@ class GUIProcess(QObject):
                 message.error(stderr.strip())
 
         if status == QProcess.CrashExit:
-            exitinfo = "{} crashed!".format(self._what.capitalize())
+            exitinfo = "{} crashed.".format(self._what.capitalize())
             message.error(exitinfo)
         elif status == QProcess.NormalExit and code == 0:
             exitinfo = "{} exited successfully.".format(
diff --git a/tests/unit/misc/test_guiprocess.py b/tests/unit/misc/test_guiprocess.py
index 4ed19f64e..e86eda5c4 100644
--- a/tests/unit/misc/test_guiprocess.py
+++ b/tests/unit/misc/test_guiprocess.py
@@ -237,6 +237,18 @@ def test_exit_unsuccessful(qtbot, proc, message_mock, py_proc, caplog):
     assert msg.text == expected
 
 
+def test_exit_crash(qtbot, proc, message_mock, py_proc, caplog):
+    with caplog.at_level(logging.ERROR):
+        with qtbot.waitSignal(proc.finished, timeout=10000):
+            proc.start(*py_proc("""
+                import os, signal
+                os.kill(os.getpid(), signal.SIGSEGV)
+            """))
+
+    msg = message_mock.getmsg(usertypes.MessageLevel.error)
+    assert msg.text == "Testprocess crashed."
+
+
 @pytest.mark.parametrize('stream', ['stdout', 'stderr'])
 def test_exit_unsuccessful_output(qtbot, proc, caplog, py_proc, stream):
     """When a process fails, its output should be logged."""